1. Technical Field
The present invention relates to distance vector routing in packet switching communication networks, such as in a wireless mobile ad hoc network (MANET).
2. Background
Networks of general purpose computer systems and specialized devices connected by external communication links are well known and widely used in commerce. The networks often include one or more network devices that facilitate the passage of information between the computer systems and devices. A network node is a network device or computer or specialized device connected by the communication links. An end node is a node that is configured to originate or terminate communications over the network. An intermediate network node facilitates the passage of data between end nodes.
Communications between nodes are typically effected by exchanging discrete packets of data. Information is exchanged within data packets according to one or more of many well known, new or still developing protocols. In this context, a protocol consists of a set of rules defining how the nodes interact with each other based on information sent over the communication links.
Routers are intermediate network nodes that support the exchange of data packets across multiple heterogeneous subnetworks. Routing protocols are used by routers to pass information that affects the links chosen by each router to forward a data packet. Some routing protocols require routers to exchange information about all connections at each router. Distance vector routing protocols require a router to pass only summary information that indicates a destination in the network and a total cost (called a distance) of reaching that destination from the router.
In emerging mobile networks, such as mobile ad hoc networks, communication bandwidth between routers can be scarce, while routing information is likely to change quickly, at least some of the time, as mobile nodes move into and out of direct communication with each other. Depending on the radio characteristics of the communicating nodes, some communication is two way (each can send and receive to the other) and some is one way (e.g., the node with a weaker transmitter can only receive from the other node and not send to it). It is very uncommon to use a one-way link for routing.
On demand routing protocols conserve bandwidth by passing routing information only when needed to forward a particular data stream of one or more packets of data. Such routing protocols may be perceived as slow to establish a connection. Proactive routing protocols use the time between data packets to pass routing information changes so that each router already has a path to each destination in the network. Such protocols may be perceived as faster to establish a connection, but may consume extra bandwidth for route maintenance, which slows the perceived duration of transmitting a data stream.